Ring-shaped getter with top deflector, for improving and/or keeping up vacuum in electronic tubes



Dec. 28, 1965 P. DELLA PORTA 3,225,911

RINGSHAPED GETTER WITH TOP DEFLECTOR. FOR IMPROVING AND/OR KEEPING UP VACUUM IN ELECTRONIC TUBES Filed Aug. 10. 1961 5 Sheets-Sheet 1 FIG.3

Dec. 28, 1965 P. DELLA PORTA 3,225,911

RING-SHAPED GE'I'TER WITH TOP DEFLECTOR. FOR IMPROVING AND/OR KEEPING UP VACUUM IN ELECTRONIC TUBES Filed Aug. 10, 1961 5 Sheets-Sheet z E c m E r 8 u 1 9 LL.

01 E m j l l 2 ow 00 E i m (\l ch E m J T 0 E m c? (\l 9 LL Dec. 28, 1965 P. DELLA PORTA 3,225,911

RING-SHAPED GETTER WITH TOP DEFLECTOR. FOR IMPROVING AND/OR KEEPING UP VACUUM IN ELECTRONIC TUBES Filed Aug. 10, 1961 3 Sheets-Sheet 5 J CD 4 9 LL.

I I I Q LL.

IJ I I 'L L L I United States Patent 3,225,911 RING-SHAPED GETTER WITH TOP DEFLECTOR,

FOR IMPROVING AND/ OR KEEPING UP VACU- UM IN ELECTRONIC TUBES Paolo Della Poi-ta, Via Gallarate 215, Milan, Italy Filed Aug. 10, 1961, Ser. No. 131,059 6 Claims. (Cl. 206--.4)

In cathode ray electron tubes as used as television tubes or Oscilloscopes, vacuum is improved by means of getters, generally evaporated barium getters.

The barium amounts used are comparatively great, of

from 30 to 100 mg. of barium in tubes with one electron gun, somewhat more in tubes with three electron guns or in special tubes.

The present invention is illustrated in the accompanying drawings wherein:

FIGS; 1a, 1b, 1c and 1d are schematic views of four television tubes having diflerent shapes;

FIGS. 2a, 2b and 2c are schematic views of television tubes having three different directional fins and having a graph for each tube related to common ordinate and abscissa axes;

FIG. 3 is a vertical cross section of a ring-shaped getter and deflector;

FIG. 4 is a vertical cross section of a modification of FIG. 3;

FIG. 5 is a vertical cross section of a modification of FIG. 4;

FIG. 6 is a vertical cross section of a modification of FIG. 5;

FIGS. 7a, 7b and 7c are schematic views for three different annular getters and having accompanying graphs with common ordinate and abscissa axes; and

FIG. 8 is a vertical cross section of a ring-shaped getter and deflector with a supporting tongue.

Modern technique has required the construction of television tubes being shorter with equal useful surface area of the images. In FIGS. 1a, lb, 1c and 1d of the accompanying drawings there are illustrated the shapes of the tube of 70, 90, 110 and 1:14". In those figures 1 indicates the getter placed in the neck 3 of the tube, above the electron gun 2, with 4 the cone and with 5 the ceiling of the tube.

The getter is made to evaporate in the final stage of the process of manufacturing the tube, in some case while it is still attached to the pump, more often when it has already been closed. For a good absorption of the gases by the barium mirror it is necessary that the latter be developed over the maximum surface possible. The zone of the neck, where the electron gun is, is not available for the barium deposit and on the contrary barium must be kept far away for reasons of insulation. With the shortening of the tubes the surface area available on the tube neck above the electron gun is so reduced that it has become necessary to begin with depositing the barium also on the bulb, namely on the part where the fluorescent material is deposited and on the cone. This new technique has been possible since for reasons of luminosity of the tube, the technique of aluminating the tube has been adopted. With such technique the fluorescent material is practically protected from the attack of the barium by means of a thin aluminum film.

The barium deposit superimposed over the aluminum deposit, which itself is little uniform, is however a brake to the electrons, which leaving the gun are to attain the fluorescent material to make it luminous. When the energy of the electrons is low and the thickness of the barium is too great, there is created a less luminous zone at the centre of the fluorescent screen, the so-called central spot. Even if things do not go so far as that, an excessive barium deposit reduces the brilliancy of the tube.

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Hence it is imperative to have a distribution as uniform as possible of the barium On the fluorescent screen. In FIGS. 2a, b, c, there are illustrated the results in this respect which are obtained with various known getters, namely in FIG. 2a with the ring-shaped getter with straight directional fins according to Patent No. 2,824,640; in FIG. 2b with ring-shaped getters with directional fins slanting towards the interior of the ring, and in FIG. 2c with ring-shaped getters with directional fins slanting towards the exterior of the ring, according to Patent No. 2,907,451.

In all of the three cases, the amounts of barium evaporated were 28 mg. 'In the figures are indicated the barium deposits on the neck 3, on the cone 4 and on the ceiling 5 of the tubes in mg. as for the distribution over the three parts 3, 4, 5 of the tube, and moreover in Angstrom as for the distribution of the part distributed on the ceiling 5 of the tube. These results, which are fairly satisfying, however are not obtained with these known getters when the amount of evaporated barium increases up to more than 40 mg, in which case one gets too strong a concentration of barium in determined zones for instance at the centre of the ceiling of the tube.

Present-day technique of production of tubes with shorter and shorter pumping times, the use of higher and higher voltages which, if they make the problems of barium distribution less critical, however make the emission of gas under electron bombardment higher, the requirements of life duration of the tubes these all are factors which often require the use of getters of barium heavier and heavier, namely with evaporation of amounts of 60 to 70 mg. of barium in 17 and 19" tubes.

It is an object of the present invention to solve these problems by providing a type of ring-shaped getter which permits the deposit of strong amounts of barium 'with a satisfactory distribution thereof in the tubes, namely without an excessive thickness at the centre of the fluorescent screen and with -a good distribution over the cone, avoiding barium vapours on the gun. To solve that problem, a ring-shaped getter of a type known per se from the above cited patents, is equipped according to the invention with a deflector placed above the annular container, in such a Way that the barium vapours leaving said container are directed slantingly upwards, partly towards the interior of the ring and partly towards the exterior of the container ring. The getter according to the present invention, there fore, represents a combination of the annular getter of FIGS. 2b and 2c namely with evaporation towards both the interior and the exterior of the ring, avoiding instead the direct evaporation upwards.

FIGURES 3 to 6 illustrate various embodiments of the getter according to the present invention. In FIG. 3 there is illustrated a ring-shaped getter 1 having U-shaped cross-section, combined with a deflector 6 in the shape of a wide open V. FIG. 4 illustrates an embodiment of a ringshaped getter having U-shaped cross-section, with directional fins bent outwards and with a deflector element having a cross-section in the shape of a channel. that creates two annular slits as outlets for the vapours from the getter, of which one directed slantingly upwards and inwards and the other one slantingly upwards and outwards with respect to the getter. The deflector is placed centrally upon the annular getter in such a way that the two outlet slits have equal widths. According to the type of tube and to the positioning of the getter in the tube, it is also possible to make prevail the evaporation towards the exterior or that towards the interior, by means of an inwardly (FIG. 5) or outwardly (FIG, 6) displaced position of the deflector with respect to the container below.

The results of the distribution of barium with these annular getters with top deflector, according to FIGS. 3 and 4, as compared with the known annular getter, are

illustrated in FIGS. 7a, 7b and 7c. The amount of evaporated barium has been in the three cases illustrated, of about 60 mg. As can be .seen in said figures, the barium deposit on the ceiling of the tube, indicated in Angstrom, has a strong peak at the center with the tube with usual annular getter, as shown in FIG. 7a, while said peak is much lower with getter types according to the present invention as shown in FIGS. 7b and 7c and, therefore, the distribution of barium is more uniform. The same FIG- URES 7a, b, c, also show that with the usual annular getter type the deposit of barium on the cone of the tube is quite scarce (FIG. 7a), while it is stronger with getter types according to the invention, as FIGS. 7b and 70 show. The better distribution of barium in the tube is apparently obtained with the getter according to FIG. 70.

It will be understood that many other ring-shaped getter forms and forms of deflector arrangements thereabove may be proposed. The deflector may be provided with the shaping of the container or, better, it may be fitted after finishing the getter; by means of clamping or welding between the container and the deflector. FIG. 8 shows by Way of example an embodiment wherein a tongue 7 is welded to the container as well as to the deflector and serves as a support for the getter in the tube.

FIG. 8 also illustrates the filling of the container 1 with evaporated gettering material, and the filling of the deflector, the latter too being made as a container of ring and channel shape with non-evaporated gettering material, so as to provide a mixed getter.

In the same way, the deflector 6 made in the shape of a container might be filled with aluminium or other metal which is to be evaporated prior to barium or together with barium to make directly the met-allizing of the tube in the final stage of pumping said tube.

It will be understood that in this case the containerdefiector 6, should be built with material adapted to resist the attack of A1 and of high temperatures. The metal to be evaporated however may even come from the reaction of an alloy prepared for that purpose in the container-deflector.

What I claim is:

1. Getter means for selectively controlling the distribu-,

tion of getter material over the interior surface area of a vacuum tube comprising an annular trough having an open upper periphery adapted to contain an evaporable getter material, and an annular deflector means immediately above and substantially coextensive with said open upper periphery of said trough, said deflector means being so shaped and so proportioned relative to said trough as to form internally and externally disposed peripheral exhaust slits between said trough and said deflector means.

2. The invention defined in claim 1, wherein the relative physical dimensions of said exhaust slits are pre selected to thereby control the distribution of vapors from said evaporable getter material over -a given internal geometry of a vacuum tube in which said getter means is incorporated.

3. The invention defined in claim 1, wherein said deflector means comprises a second annular trough, said second trough being adapted to contain a non-evaporable getter material.

4. The invention defined in claim 1, wherein said deflector means is V-shaped in cross-section.

5. The invention defined in claim 1, wherein said deflector means is channel-shaped in cross-section.

6. The invention defined in claim 1, wherein said deflector means comprises a second annular trough, and an evaporable metal in said second trough, whereby means is provided for directly metallizing a vacuum tube during gettering thereof.

References Cited by the Examiner UNITED STATES PATENTS 2,422,427 6/1947 Louden 313-481 2,869,014 1/1959 Natalis 313-181 3,023,883 3/1962 Meisen 2 06-0.4

FOREIGN PATENTS 736,475 9/ 1955 Great Britain.

THERON E. CONDON, Primary Examiner.

RALPH G. NILSON, Examiner. 

1. GETTER MEANS FOR SELECTIVELY CONTROLLING THE DISTRIBUTION OF GETTER MATERIAL OVER THE INTERIOR SURFACE AREA OF A VACUUM TUBE COMPRISING AN ANNULAR TROUGH HAVING AN OPEN UPPER PERIPHERY ADAPTED TO CONTAIN AN EVAPORABLE GETTER MATERIAL, AND AN ANNULAR DEFLECTOR MEANS IMMEDIATELY ABOVE AND SUBSTANTIALLY COEXTENSIVE WITH SAID OPEN UPPER PERIPHERY OF SAID TROUGH, SAID DEFLECTOR MEANS BEING SO SHAPED AND SO PROPORTIONED RELATIVE TO SAID TROUGH AS TO FROM INTERNALLY AND EXTERNALLY DISPOSED PERIPHERAL EXHAUST SLITS BETWEEN SAID TROUGH AND SAID DEFLECTOR MEANS. 